Chemical evolution. XXVI. Photochemistry of methane, nitrogen, and water mixtures as a model for the atmosphere of the primitive earth

Abstract

Methane-water vapor mixtures were irradiated using a low pressure mercury lamp and the reaction products were determined at intervals between 0.5 and 6 hr. Formaldehyde, acetaldehyde, and methanol were observed after 0.5 hr. The presence of ethylene glycol, ethanol, acetone, isopropyl alcohol, tert-butyl alcohol, methyl ethyl ketone, isobutyl alcohol, rert-amyl alcohol, and neopentyl alcohol was detected in small amounts after 2 hr and the yields increased after 4 and 6 hr irradiation times. Virtually the same product yields were obtained after irradiating a -2:l methane-water mixture as were obtained from a -1: 1: 1 methane-nitrogen-water mixture demonstrating that nitrogen does not react under these conditions. Furthermore, no amino acids were detected when nitrogen was added to the reaction mixture. The reactions are initiated by the hydroxyl radicals formed by water photolysis. These hydroxyl radicals abstract a hydrogen atom from methane as the first step in the synthesis. The prebiological significance of these photochemically generated compounds is discussed.Ultraviolet light from the sun offered the greatest potential as the energy source t o drive chemical reactions on the primitive earth. I t has been estimated that, in the absence of ozone, wavelengths less than 300 n m contributed 3400 cal c m W 2 year-' and those less than 200 n m contributed 41 cal cm-2 year-' t o t h e surface of the primitive earth.2 T h e next most abundant energy sources, electrical discharges and shockwaves are estimated to have contributed 4 and 1.1 cal Journal of the American Abstract: The relative cross section for the gas phase photodetachment of electrons has been determined for several substituted phenoxides and thiophenoxide in the wavelength region 300-530 nm (4.1 3-2.34 eV). An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions and a 1000-W xenon arc lamp with a grating monochromator was employed as the light source. The following quantities were determined: EA(o-CH3C6H40.) S= EA(CsH5O.) I 2.36 f 0.06 eV, EA(o-CIC6H40.) I 2.58 f 0.08 eV, EA(C6HsS.) I 2.47 f 0.06 eV. I t is suggested that a short wavelength portion of the photodetachment spectrum is the result of electronic excitation of the negative ions, followed by autodetachment. Recent photodetachment experiments have indicated of molecular properties. The threshold yields a vertical electron detachment energy, which in favorable cases also represents the electron affinity of the corresponding radical. Abrupt changes in the photodetachment cross section can arise from transitions to excited state^,^ thus, transition Brauman et al. / Photodetachment of Electrons f r o m Phenoxides and Thiophenoxide that complex molecular ions can exhibit unusual behavior. This appears to be particularly true for delocalized systems, such as C5H5-and C4H4N-.3%4 The photodetachment cross section of an anion can provide information about a variety

The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up

“…Two such high-temperature planetary sources are lightning and impacts, which have been contemplated as energy sources for prebiotic molecular synthesis (Chyba & Sagan 1992;Nava-Sedeño et al 2016). However, these sources face the problem of abundance: lightning and impact-driven shockwaves are estimated to have delivered three orders of magnitude less energy than UV photons ( 300 nm < ) to the young Earth (Ferris & Chen 1975). Hence, it is difficult to avoid the conclusion that a paucity of UV light might pose a problem for abiogenesis scenarios on M-dwarf planets like Proxima Centauri b, LHS 1140b, or the TRAPPIST-1 planets.…”

Nitrogen Incorporation in CH4-N2 Photochemical Aerosol Produced by Far Ultraviolet Irradiation

“…Interestingly, when other workers in the 1970s and early 1980s attempted to repeat the results of Dodonova (1966) but failed to produce nitriles or N-containing organics in the UV (Ferris and Chen, 1975;Chang et al, 1979;Bossard et al, 1982;Raulin et al, 1982), Bossard et al (1982) concluded that ''UV light is not able to produce nitriles from CH 4 -N 2 mixtures'' and ''UV light is not an efficient source for producing unsaturated carbon chains.'' The results presented herein clearly contradict those conclusions.…”

Marine Hydrothermal Systems and the Origin of Life

“…Fe 2 + in a cyclotron yields traces of CH20 and formic acid (Garrison et al, 1951). CH20 and higher aldehydes are also formed by the photolysis of H20 in the presence of C~ (Ferris and Chen, 1975b;Bar-Nun and Chang, 1983), the photolysis of CO-H20 mixtures (park and Getoff, 1988) and the photolysis of methanol (Allamandola et al, 1988). It has been tentatively identified as a product of the photolysis of ferrous carbonate (Joe et al, 1986) and~-irradiation of calcium carbonate (Albarran et al, 1987).…”